Sergei A. Voloshin Wayne State University, Detroit, Michigan

1. What can we learn about proton structure? Sergei A. Voloshin Wayne State University, Detroit, Michigan • Goal of presentation: Share my own interests. Find out what other people are interested in. • My interest: what is the role of constituent quarks in hadronic physics? (assuming they do exist) This question splits into two: • Role of constituent quark stage in the hadronization process. • b) Can we “see” the constituent quarks structure of the proton? page

2. Scales of hadronic physics Levin – Frankfurt (1965), Lipkin – Sheck (1966): Experimentally ~ 1/1.6 Shrinkage of the diffraction cone (== effective radius increase with energy): The first scale – 0.6-1.0 fm ~-1QCD – typical hadron radius (radius of confinement). - Radius of small size instantons – sets const. quark radius. Additive quark model: (hadron spectroscopy, magnetic moments, etc.) Primordial kTin lepton pair and large pt production ~ 1-2 GeV  • Kovner - Wiedemann (PRD 66:034031, 2002): • Total cross section grows for two reasons: • Increase in parton density (“darkness”) –described by “hard” Pomeron. • Increase in radius (soft Pomeron) – asymptotically saturates Froissart bound (?). page

3. What would be the consequences of such a structure? The first one – the possibility to have 1, two, or three “string” interactions (collisions of pairs of constituent quarks) Q. to Rolf: why the tails of “sigma_3” distributionare not shown (at least as far as for “sigma_1”? page

4. Higher energies ==> cleaner separation of multiple collisions Need for a trigger for high multiplicity events? Already in? page

5. Mean pt, two-particle pt and azimuthal correlations Azimuthal correlations: will we be ableto observe rescatterings of particles from two qq collisions? Anisotropic source by HBT? page

6. Parton spatial distribution: How much of black vs gray? What defines the value of the uncorrelated background? Why is it larger then determined byinclusive single particle spectrum,which would correspond to the caseof independent hard collisions? We can study this by looking at double hard collisions! … Anyway, maybe you are right and one should think harder about why they are what they are, assuming that we can somehow extract them from the data with defensible error bars. Peter [Jacobs] page

7. What defines the probabilities of multiple hard collisions? The values of the background larger than defined by inclusive single particle spectrum meansthat the probability of two hard collisions is larger than the square of probabilities ofsingle hard collision. If hard collisions happen only in the overlap region of area A, then Surprisingly (for me) for two overlapping discsand average over bdb, this ratio is rather large, 4 - 64/(32) 1.84 , … but still lower than the (STAR) experimental value,of about 2.5 page

8. Toward measuring constituent quark size... Consider a case when more energetic partons are distributedin a region occupying only a fraction q of the total areaover which softer partons are distributed. Then ?? page

9. Summary Study of ”plain” multiparticle production can bring exciting physics. page